The invention relates generally to a rotating blade for use in a turbomachine. More particularly, the invention relates to a rotating blade including a part span shroud having a hollow portion therein, the blade further including an optimized fillet size.
The fluid flow path of a turbomachine such as a steam or gas turbine is generally formed by a stationary casing and a rotor. In this configuration, a number of stationary vanes are attached to the casing in a circumferential array, extending inward into the flow path. Similarly, a number of rotating blades are attached to the rotor in a circumferential array and extend outward into the flow path. The stationary vanes and rotating blades are arranged in alternating rows so that a row of vanes and the immediate downstream row of blades form a stage. The vanes serve to direct the flow path so that it enters the downstream row of blades at the correct angle. Airfoils of the blades extract energy from the working fluid, thereby developing the power necessary to drive the rotor and the load attached thereto.
The blades of the turbomachine may be subject to vibration and axial torsion as they rotate at high speeds. To address these issues, blades typically include part span shrouds disposed on the airfoil portion at an intermediate distance between the tip and the root section of each blade. The part span shrouds are typically affixed to each of the pressure (concave) and suction (convex) sides side of each airfoil, such that the part span shrouds on adjacent blades matingly engage and frictionally slide along one another during rotation of the rotor. Part span shrouds having solid construction have greater weights and typically require larger fillets to ease structural stress between the part span shroud and the airfoil surface and to support the part span shroud on the airfoil. This tends to result in less aerodynamic blades, and therefore a decrease in flow rate and overall performance of the turbomachine.